Multi-speed automotive transmission using paired helical gearing

ABSTRACT

A multi-speed transmission suitable for automotive-type use employs paired helical gears. For each speed of the transmission, at least one pair of helical cut gears is mounted on an input drive shaft for engaging and mating at least one pair of helical cut gears mounted on an idler shaft. During load transmission for a given speed, the helical gear pairs on the idler shaft center themselves on the helical gear pairs on the drive shaft to balance load transmission amongst gears. The idler shaft would also have at least one pair of helical cut gears to engage and mate at least one pair of helical cut gears on a power output shaft.

FIELD OF THE INVENTION

The present invention is directed to improvements in multi-speedtransmissions suitable for automotive uses. More particularly, thepresent invention is directed to a multi-speed transmission using pairedhelical gears wherein a compact transmission can be provided havingincreased power capacity compared to a conventional transmission.

BACKGROUND OF THE INVENTION

Gear transmissions having pairs of helical gears mounted on a driveshaft for engagement with respective pairs of helical gears mounted on adriven shaft resulting in even load sharing amongst gears are disclosedin copending U.S. patent application Ser. No. 09/167,760 filed Oct. 7,1998 which is a continuation application under 35 U.S.C. §120 of pendingapplication Ser. No. 09/021,622 filed Feb. 9, 1998, both of thepreceding applications being entitled IMPROVEMENTS IN POWER SHARING GEARSETS. The disclosures, including the disclosures of the specificationand drawings of prior U.S. patent application Ser. No. 09/167,760 filedOct. 7, 1998 and Ser. No. 09/021,622 filed Feb. 9, 1998 are herebyexpressly incorporated by reference into this present application.

Paired helical gearing permits, as a practical matter, power sharingamong multiple gears on a single shaft. Prior to the invention of pairedhelical gearing, very precise tolerances were required to successfullyconstruct a transmission which had multiple gears on a common shaft.Therefore, prior to the invention of paired helical gearing,transmissions with multiple gears on a single shaft were for mostpurposes commercially impractical.

A major commercial application for paired helical gearing istransmissions that have constraints on the size of the diameter of gearsdue to space limitations, but which are also required to transmitsignificant power.

The present invention is directed to the use of paired helical gearingto provide for multi-speed transmissions suitable for automotive use. Inthe present application, transmissions for automotive use includeswithin its meaning, but is not limited to, uses in automobiles, trucks,farm equipment, earth moving equipment, ships, boats and the like.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a multi-speedautomotive transmission that employs paired helical gearing.

It is also an object of the present invention to provide a multi-speedautomotive transmission that is compact in size but has a high powercapacity.

These and other objects of the present invention will become apparentfrom the following description and claims read in conjunction with thedrawings.

SUMMARY OF THE INVENTION

The present invention is directed to a multi-speed transmission suitablefor automotive-type uses. The transmission comprises an input driveshaft and idler shafts. Each speed of the transmission is provided by atleast one pair of helical cut drive gears mounted on the drive shaftbeing engaged and mated by at least one pair of helical cut driven gearsmounted on an idler shaft. The hand or the sense of the drive and drivenhelical cut gear pairs is selected so that upon engagement and mating ofa selected pair of drive and driven helical cut gears for a giventransmission speed, thrust forces are created to cause the pair ofdriven helical cut gears mounted on the idler shaft to move toward oneanother. The selected pair of driven helical gears mounted on the idlershaft also move together on the idler shaft to center themselves on therespective drive helical gears on the input drive shaft to balance theload and to provide for an approximate equal sharing of the transmittedload amongst gears.

For uses requiring large transmissions of power, for each speed of thetransmission, two or more pairs of helical cut gears may be provided onthe drive shaft for being engaged respectively by two or more pairs ofhelical cut gears provided on the idler shaft.

An output shaft is provided having mounted thereon one or more pairs ofhelical cut driven gears for rotating the output shaft. The idler shafthas mounted thereon one or more pairs of drive output helical cut gearsrotated by the idler shaft and for engaging and mating the one or morehelical gear pairs mounted on the output shaft for transmission of powerto the output shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings forming part hereof:

FIG. 1 is a schematic view of one embodiment of an automotivetransmission in accordance with the present invention illustrating afour speed transmission using for each speed of the transmission onepair of paired helical gears on an input drive shaft and one pair ofpaired helical gears on an idler shaft.

FIG. 2 is a schematic view of another embodiment of an automotivetransmission in accordance with the present invention illustrating a twospeed transmission using for each speed of the transmission two pairs ofpaired helical gears on an input drive shaft and two pairs of pairedhelical gears on an idler shaft.

FIG. 3 is a schematic cross-sectional view along line 3—3 of FIG. 1.

FIG. 4 is a schematic cross-sectional view along line 4—4 of FIG. 2.

FIG. 5 is a schematic view of one embodiment of a shifting mechanismsuitable for use with the transmission of the present invention.

FIG. 6 is a schematic side view of a shifting fork used in the shiftingmechanism illustrated in FIG. 5.

FIG. 7 is a schematic cross-sectional view illustrating an alternativeembodiment of the output drive helical gears illustrated in FIGS. 1 and2 wherein the output drive helical gear mounted on a first idler shafthas a different outside diameter than the output drive helical gearmounted on a second idler shaft and the axis of output shaft is locatedin a different plane than the axis of the of the first idler shaft andthe axis of the second idler shaft.

DETAILED DESCRIPTION

In order to provide a more complete understanding of the presentinvention and an appreciation of its advantages, a detailed descriptionof preferred embodiments is now provided with reference to the drawings.

FIG. 1 schematically illustrates one embodiment of an automotive ormulti-speed transmission, in accordance with the present invention,which provides for four speeds. In the embodiment of FIG. 1, one pair ofdrive helical gears on a drive input shaft engages one pair of drivenhelical gears on an idler shaft to provide for each transmission speed.

The multi-speed automotive type transmission of FIG. 1 comprises a inputdrive shaft 1, two idler shafts 2 and 3, and an output shaft 4. Theembodiment illustrated in FIG. 1 provides for four speeds. However, thepresent invention is not limited to the use of only two idler shafts. Ifdesired, as many idler shafts may be employed as can be fit around theinput shaft, thus allowing for a multitude of speeds. Similarly, in theembodiment illustrated in FIG. 1, only two pairs of helical drive gearsare illustrated mounted on the input drive shaft 1. The number of speedsavailable may be increased by increasing the number of drive helicalgear pairs mounted on the input drive shaft and correspondinglyincreasing the number of driven helical gear pairs mounted on the idlershafts.

With reference to FIG. 1, input drive shaft 1 has a first end 31 and asecond end 32. First end 31 of input drive shaft 1 is connected to aprime mover, such as an automobile internal combustion engine (notillustrated), for rotation by the prime mover. In the embodimentillustrated, the prime mover rotates the input drive shaft 1 in theclockwise direction as illustrated by the arrow. As will be appreciated,a prime mover, such as an automobile internal combustion engine, willalways rotate the input drive shaft in the same direction.

Mounted for rotation on input drive shaft 1 are a first pair of drivehelical gears 5 a, 5 b and a second pair of drive helical gears 6 a, 6b. In the embodiment of FIG. 1, drive helical gear pairs 5 a, 5 b and 6a, 6 b are mounted on input drive shaft 1 for rotation by input driveshaft 1 and they are also fixedly mounted to input drive shaft 1 so thatthey cannot move in the axial direction of input drive shaft 1. As willhereinafter become apparent, it is only functionally necessary thatdrive helical gears of each pair be restrained from separating from oneanother in the axial direction of input drive shaft 1. In the embodimentillustrated in FIG. 1, the outside diameter of drive helical gear pair 5a, 5 b is greater than the outside diameter drive helical gear pair 6 a,6 b.

Located parallel to input drive shaft 1 are first idler shaft 2 andsecond idler shaft 3. Driven helical gear pair 7 a, 7 b is mounted onfirst idler shaft 2 to rotate first idler shaft 2 when driven helicalgear pair 7 a, 7 b engages and mates with drive helical gear pair 5 a, 5b. Driven helical gear pair 8 a, 8 b is mounted on first idler shaft 2to rotate first idler shaft 2 when driven helical gear pair 8 a, 8 bengages and mates with drive helical gear pair 6 a, 6 b.

Driven helical gear pair 9 a, 9 b is mounted on second idler shaft 3 torotate second idler shaft 3 when driven helical gear pair 9 a, 9 bengages and mates with drive helical gear pair 5 a, 5 b. Driven helicalgear pair 10 a, 10 b is mounted on second idler shaft 3 to rotate secondidler shaft 3 when driven helical gear pair 10 a, 10 b engages and mateswith drive helical gear pair 6 a, 6 b.

Driven helical gear pairs 7 a, 7 b; 8 a, 8 b; 9 a, 9 b; and 10 a, 10 bare also mounted on their respective idler shafts 2 and 3 for axialmovement on the respective idler shaft. In the embodiment illustrated inFIG. 1, this axial movement is provided for by idler shafts 2 and 3being spline shafts with the respective driven helical gear pairs beingsplined to their respective idler shaft. The spline idler shafts firmlyrotationally link the driven helical gears to the spline shaft but alsoallow axial movement of the driven helical gears on the spline shaft.

FIG. 3 is a schematic cross-section along line 3—3 of FIG. 1 andillustrates driven helical gear 8 b splined to idler shaft 2 and drivehelical gear 6 b fixedly mounted to input drive shaft 1 whereby thedrive helical gear 6 b does not move in the axial direction of the inputdrive shaft 1. In the non-limiting example illustrated in FIG. 3, drivehelical gear 6 b and input drive shaft 1 are machined from the samestock of material. In the embodiment illustrated in FIG. 1, the idlershafts are spline shafts and the driven helical gear pairs are splinedto the idler shafts for axial movement on their respective idler shaft.However, the present invention is not limited to use of a spline shaftarrangement for the idler shafts. Any mechanical design, e.g., a keyeddesign, which permits appropriate axial movement of a respective drivenhelical gear pair on a respective idler shaft would be within the scopeof the present invention. Likewise, any mechanical design which preventsdrive helical gear pairs mounted on the input drive shaft fromseparating from one another in the axial direction of the input driveshaft during force transmission would be within the scope of the presentinvention.

It will be apparent to one skilled in the art that the embodimentillustrated in FIG. 1 provides for four speeds, i.e., gears 7 a, 7 bengaging and mating gears 5 a, 5 b; gears 9 a, 9 b engaging and matinggears 5 a, 5 b; gears 8 a, 8 b engaging and mating gears 6 a, 6 b; andgears 10 a, 10 b engaging and mating gears 6 a, 6 b. It will also beapparent to one skilled in the art, by way of example, in theillustrated embodiment of FIG. 1, the diameter of driven helical gears 8a, 8 b is larger than the diameter of drive helical gears 6 a, 6 bthereby providing for a rotational speed reduction or step down. On theother hand, the diameter of driven helical gears 9 a, 9 b is smallerthan the diameter of drive helical gears 5 a, 5 b, thereby providing fora rotational speed increase, a step up or overdrive. It will be apparentthat the gear ratios for each speed may be varied, as desired, by oneskilled in the art as required by the intended use of the transmission.

Drive helical gear 5 a and drive helical gear 5 b each have a helicalcut at the same angle but in the opposite sense (or opposite hand) toone another. Driven helical gear 7 a and driven helical gear 9 a eachhave a helical cut at the same angle but in the opposite sense (oropposite hand) to the helical cut of drive helical gear 5 a. Drivenhelical gear 7 b and driven helical gear 9 b each have a helical cut atthe same angle but in the opposite sense (or opposite hand) to thehelical cut of drive helical gear 5 b. The sense of the angle of thehelical cuts is such that a thrust force is developed wherein drivenhelical gears 7 a, 7 b or 8 a, 8 b will move toward each other in theaxial direction of the respective idler shaft when input shaft 1 isrotated by the prime mover and they are respectively engaged and matedby drive helical gear pair 5 a, 5 b. Likewise, the sense of the angle ofthe helical cuts develops a thrust force such that when the input shaft1 is rotated by the prime mover, if drive helical gear pair 5 a, 5 b isengaged and mated with either driven helical gear pair 7 a, 7 b or 9 a,9 b, drive helical gear pair 5 a, 5 b will be subjected to forceswanting to spread helical gears 5 a, 5 b apart from one another in theaxial direction of input drive shaft 1. However, as previouslydiscussed, helical gears 5 a and 5 b do not actually move in the axialdirection of input drive shaft 1 because they are fixedly mounted toinput drive shaft 1 to prevent such axial movement.

The sense of the angle of the helical cut for drive helical gear pair 6a, 6 b and driven helical gear pairs 8 a, 8 b and 10 a, 10 b are thesame as described with respect to drive helical gear pair 5 a, 5 b anddriven helical gear pairs 7 a, 7 b and 9 a, 9 b. That is when eitherdriven helical gear pair 8 a, 8 b or 10 a, 10 b engages and mates withdrive helical gear pair 6 a, 6 b thrust force developed by the rotationof input drive shaft 1 by the prime mover will cause either drivenhelical gear pair 8 a, 8 b or driven helical gear pair 10 a, 10 b, tomove toward each other, as the case may be, in the axial direction ofthe respective idler shaft. Likewise, forces will be created wanting tospread drive helical gears 6 a, 6 b apart from one another in the axialdirection of the input drive shaft 1, but again, drive helical gears 6a, 6 b do not move in the axial direction because they are fixedlymounted to the input drive shaft 1 to prevent such movement.

In the embodiment illustrated in FIG. 1, driven helical gear pair 8 a, 8b is engaged and mated with drive helical gear pair 6 a 6 b. Input driveshaft 1 rotates drive helical gear pair 6 a, 6 b which rotate drivenhelical gear pair 8 a, 8 b which in turn causes idler shaft 2 to rotate.In the illustrated embodiment, input drive shaft 1 rotates in theclockwise direction and idler shaft 2 rotates in the counter clockwisedirection. All other driven helical gear pairs on idler shafts 2 and 3are disengaged from their respective drive helical gear pair on theinput drive shaft 1.

As previously discussed the sense of the angle of the helical cut ondriven gears 8 a, 8 b creates thrust forces due to rotation which causegears 8 a and 8 b to move toward each other in the axial direction ofthe idler shaft 2. A spacer member 21 between gears 8 a and 8 b preventsthe side of gear 8 a facing the second end 34 of idler shaft 2 fromabutting the side of gear 8 b facing the first end 33 of idler shaft 2.Spacer member 21, as illustrated, is a cylindrical collar mounted onidler shaft 2 in such a way as to permit cylindrical collar 21 to movein the axial direction of the idler shaft 2. There is no need to splinecylindrical collar 21 to idler shaft 2. It need only be mounted on theidler shaft 2 loose enough to slide along the shaft. The forces createdby rotation also cause driven helical gears 8 a, 8 b which are beingpressed against one another but remain separated by the collar spacer 21to move together in the axial direction of the idler shaft 2 to centerdriven helical gears 8 a, 8 b with respective drive helical gears 6 a, 6b so that load transmitted from 6 a to 8 a and 6 b to 8 b is balanced.That is, there is an approximate equal load sharing.

The spacer 21 creates a gap between the inner faces of gears driven 8 aand 8 b when the gears are loaded and forced together as describedabove. This gap prevents contact between driven gear 8 a and drivinggear 6 b, or driven gear 8 b and driving gear 6 a from occurring. Thatis, if due to manufacturing inaccuracies, driven helical gear pair 8 aand 8 b move a substantial distance axially relative to drive pair 6 aand 6 b while centering opposite the drive pair, driven gear 8 a couldcontact drive gear 6 b, or alternatively, driven gear 8 b could contactdrive gear 6 a, were there insufficient space between the gears toprevent such contact. Such contact would result in failure of thecontacting gears.

The foregoing discussion with respect to driven helical gear pair 8 a, 8b engaging and mating drive helical gear pair 6 a, 6 b would apply todriven helical gear pair 7 a, 7 b engaging and mating drive helical gearpair 5 a, 5 b; driven helical gear pair 9 a, 9 b engaging and matingdrive helical gear pair 5 a, 5 b; and driven helical gear pair 10 a, 10b engaging and mating drive helical gear pair 6 a, 6 b.

A detailed discussion of the operation of paired helical gears subjectedto rotation and load may be found in the previously referenced Ser. No.09/167,760 and Ser. No. 09/021,662.

The previously discussed spacer or collar member 21 is only by way ofillustration. The collar member 21 could be replaced with projections onthe sides of gears 8 a, 8 b facing one another. The transmission wouldalso operate if gears 8 a and 8 b were permitted to abut one another, aslong as there was a sufficient gap between driving gears 6 a and 6 b toprevent the above-mentioned contact between gears 6 a and 8 b or 6 b and8 a. The preferred spacing between the sides of gears 8 a and 8 bdepends upon the expected relative axial movement between the drive anddriven gear pairs. In practice, a gap of about 1 or 2 mm would suffice.This would also apply to gear pairs 7 a, 7 b; 9 a, 9 b; and 10 a, 10 b.There would also be, preferably, a spacer, such as collar 21, locatedbetween gear pairs 7 a, 7 b; 9 a, 9 b; and 10 a, 10 b (not illustrated).The same considerations would apply to the spacing between fixed drivehelical gears 6 a, 6 b and 5 a, 5 b.

In another embodiment of the present invention, a multi-speedtransmission could be provided using a drive input shaft and just oneidler shaft. For example, with reference to FIG. 1, if idler shaft 2 wasthe only idler shaft present, a two speed transmission would beprovided, in accordance with the present invention, wherein each speedof the transmission comprises one pair of paired helical cut gears onthe input drive shaft and one pair of paired helical cut gears on theidler shaft. It will be appreciated that a plurality of speeds could beprovided using one input drive shaft and one idler shaft wherein eachspeed of the plurality of speeds of the transmission comprised one pairof paired helical cut gears on the input drive shaft and one pair ofpaired helical cut gears on the single idler shaft.

Engagement or disengagement of the gears is caused to take place by thepushing together or spreading apart of the driven helical gear pairs onthe respective idler shafts so that a given driven helical gear pair iseither engaged or disengaged with its respective helical drive gear pairon the input drive shaft 1. This axial spreading and pushing together ofthe driven helical gear pairs for engagement or disengagement can beaccomplished by mechanical, hydraulic or electromechanical actuatorsworking through shifting forks linked to the outside faces of the drivenhelical gears on the idler shafts. An illustrative example willhereinafter be set forth.

As can be seen by reference to FIG. 1, the driven helical gear pairs aredisengaged from the drive helical gear pairs on the input drive shaft 1by spreading them more widely apart than the total width of theirrespective drive helical gear pair. Conversely, a driven helical gearpair on an idler shaft is engaged by forcing the pair together so thatit is engaged with its respective drive helical gear pair located on theinput drive shaft 1. If desired, changing gears can be facilitated byusing synchromesh rings on the drive helical gear pairs or the drivengear pairs. The mechanical mechanism by which gears are changed is notpart of the present invention and can be comprised of any of a largenumber of gear changing mechanical mechanisms known in the art.

In practice, a gear change would comprise the following sequence. Theprime mover (not illustrated) would be declutched from the input driveshaft 1. The currently engaged gears would be disengaged by actuatingappropriate shifting forks to spread an engaged driven helical gear pairout of engagement with a respective drive helical gear pair. Theshifting forks for a driven helical gear pair desired to be engagedwould be actuated to press this driven helical gear pair together. Theprime mover would be re-engaged to input shaft 1 by re-engaging theclutch.

FIG. 5 is a schematic illustration of an example of a shifting mechanismsuitable for use with the multi-speed transmission of the presentinvention. The shifting mechanism illustrated in FIG. 5 is anon-limiting example and does not itself form part of the presentinvention. Any known suitable shifting mechanism may be used by oneskilled in the art.

With reference to FIG. 5, driven helical gear 8 a has a circumferentialgroove and lip 40 on the side of gear 8 a facing the first end 33 ofidler shaft 2. Similarly, driven gear 8 b has a circumferential grooveand lip 40 on the side of gear 8 b facing the second end 34 of idlershaft 2. The lip and grooves 40 permit shifting forks 41 to move gears 8a, 8 b in either direction along spline idler shaft 2. The shiftingforks 41 are mounted on and move along smooth shaft 42, with shaft 42running through bushings 43. The shifting forks 41 are pushed apart orpulled together by a double acting actuator 44. The distance between theforks 41 when driven helical gears 8 a, 8 b are pushed together in theengaged position is determined by sleeve 45. The shaft 42 runningthrough sleeve 45 is illustrated by dashed lines. The sleeve 45 holdsthe shifting forks 41 apart sufficiently to insure that engaged drivenhelical gear pair 8 a, 8 b has the freedom to move axially along idlershaft 2 to center itself opposite drive helical gear pair 6 a, 6 b.Collar or spacer 21 insures that gears 8 a, 8 b have a sufficient gapbetween them when they are engaged to prevent contact between gears 6 aand 8 b, or alternatively between gears 6 b and 8 a, as described above.

FIG. 6 is a schematic side view of a shifting fork 41 used in theshifting mechanism of FIG. 5.

With further reference to FIG. 1, the multi-speed transmission of thepresent invention is also provided with an output shaft 4 which has anaxis parallel to input drive shaft 1, idler shaft 2 and idler shaft 3.Output drive helical gear pair 11 a, 11 b is mounted on spline idlershaft 2 near the second end 34 for rotation by idler shaft 2. Outputhelical gears 11 a and 11 b are also mounted on idler shaft 2 for axialmovement on idler shaft 2. Output drive helical gear pair 12 a, 12 b ismounted on spline idler shaft 3 for rotation by idler shaft 3. Outputhelical gears 12 a and 12 b are also mounted on idler shaft 3 for axialmovement on idler shaft 3. In the embodiment illustrated in FIG. 1, theoutside diameters of gear pairs 11 a, 11 b and 12 a, 12 b are the same.

Output shaft 4 has mounted thereon near first end 35 driven outputhelical gear pair 13 a, 13 b for rotating output shaft 4. Similar todrive helical gear pairs 5 a, 5 b and 6 a, 6 b, output helical gear pair13 a, 13 b is fixedly mounted on output shaft 4 so that these gears donot move in the axial direction of output shaft 4.

In the embodiment illustrated in FIG. 1, output drive helical gear pairs11 a, 11 b and 12 a, 12 b are permanently engaged with driven outputhelical gear pair 13 a, 13 b. However, gear pairs 11 a, 11 b and 12 a,12 b could be equipped with engagement mechanisms similar to those usedfor engaging and disengaging the idler shaft gear pairs 7, 8, 9, and 10,such that gear pairs 11 a, 11 b, and 12 a, 12 b could be engaged ordisengaged from output gear pair 13 a, 13 b. This would allow the idlershaft that is not being driven to be disengaged from the output shaft 4.

In the embodiment illustrated in FIG. 1, the angle of the helical cut onoutput drive helical gear pairs 11 a, 11 b and 12 a, 12 b is the samesense or same hand as on the driven helical gear pairs mounted in theidler shafts 2 and 3. Likewise, the angle of the helical cut on drivenoutput helical gears 13 a, 13 b is the same sense or the same hand asthat on the drive helical gear pairs on the input drive shaft 1. Thus,in the illustrated embodiment, rotation of the idler shaft 2 by inputdrive shaft 1 will create thrust forces causing output drive helicalgears 11 a, 11 b to move toward one another in the axial direction ofidler shaft 2. Collar 21 is located between gears 11 a and 11 b.Inter-gear spacing considerations would be the same as previouslydiscussed with respect to the driven helical gear pairs on idler shaft2.

Furthermore, in the embodiment illustrated in FIG. 1, rotation of outputdrive helical gears 11 a, 11 b by idler shaft 2 will create a thrustforce at output driven helical gears 13 a, 13 b which will want to causeseparation of output driven gears 13 a, 13 b in the axial direction ofoutput shaft 4. No actual separation takes place because output drivenhelical gears 13 a, 13 b are fixedly mounted to output shaft 4. Outputdrive helical gears 11 a, 11 b will move on output shaft 4 to centerthemselves on output driven helical gears 13 a, 13 b to balance the loadtransmission. As is apparent, output shaft 4 rotates in the samedirection as input drive shaft 1.

As an alternative embodiment, the sense or the hand of the angle of thehelical cut on output drive helical gears 11 a, 11 b and 12 a, 12 b andon output driven helical gears 13 a, 13 b could be reversed. In thisalternative embodiment, output drive helical gears 11 a, 11 b willseparate in the axial direction of idler shaft 2. This separation wouldbe restrained, e.g., by a retainer member or collar fixed to idler shaft2 on either side of output drive helical gear pair 11 a, 11 b. Forceswill be established to make output driven helical gears 13 a, 13 b wantto move toward each other in the axial direction of output shaft 4. Inthis case output gear pair 13 a, 13 b must be mounted on shaft 4 suchthat the pair is free to move axially to center itself opposite gearpairs 11 a, 11 b or 12 a, 12 b. Alternatively, gear pair 13 a, 13 b canbe fixedly mounted to shaft 4, as long as shaft 4 can freely moveaxially to accomplish the required centering of gear pair 13 a, 13 bopposite pairs 11 a, 11 b or 12 a, 12 b.

FIG. 7 illustrates an alternative embodiment, in cross-section, whereinthe outside diameter of output drive helical gear 11 b mounted on idlershaft 2 has a smaller outside diameter than the outside diameter ofoutput drive helical gear 12 b mounted on idler shaft 3. The axes ofoutput shaft 4, idler shaft 2, and idler shaft 3 remain parallel to oneanother but are located in different planes.

By altering the outside diameter of output drive helical gear pairs 11a, 11 b and 12 a, 12 b, one can vary the final ratio of all the gears.For example, if the outside diameter of output drive helical gears 11 a,11 b was made smaller, this would increase the speed reduction ratios ofgears 7 a, 7 b and 8 a, 8 b. Likewise, if the outside diameter of outputdrive helical gears 12 a, 12 b was increased in size, this woulddecrease the speed reduction ratios of gears 9 a, 9 b and 10 a, 10 b.The axes of gears 11 a, 11 b; 12 a, 12 b; and 13 a, 13 b are parallel(i.e., the axes of shafts 2, 3 and 4 are parallel), but they are notnecessarily in the same plane. If the outside diameter of gear pair 11a, 11 b and the outside diameter of gear pair 12 a, 12 b, were such thatthe desired size of gears 13 a, 13 b would not fit between gears 11 a,11 b and 12 a, 12 b, the axis of output shaft 4 could be offset from theplane formed by the axes of idler shafts 2 and 3, although all axeswould be parallel to one another. This offset would allow theaccommodation of a wide variety of sizes of gears 11 a, 11 b, 12 a, 12 band 13 a, 13 b while still allowing the respective engagement of gears11 a, 11 b and 12 a, 12 b with output shaft gears 13 a, 13 b, in thefashion described above.

More than one pair of output drive helical cut gears could be providedon each idler shaft for mating and engaging more than one pair of outputdriven helical cut gears provided on the output shaft using theteachings hereinafter set forth for the embodiment of the presentinvention illustrated in FIG. 2.

It is readily apparent to one skilled in the art that a reversing gearis accomplished by use of an additional idler shaft with its own pair ofgears driving the output shaft by another idler gear pair to causereverse rotational output direction. In the embodiment where the outsidediameters of output drive helical gears 11 a, 11 b and 12 a, 12 b aredifferent and output shaft 4 is not in the same plane as idler shafts 2and 3, a reversing gear could be provided by extending drive input shaft1 and mounting another helical cut gear pair near the end 32 of inputdrive shaft 1 which is selectively engageable and disengageable withoutput driven helical cut gears 13 a, 13 b mounted on output shaft 4.

Another embodiment of a multi-gear transmission using paired helicalgears, in accordance with the present invention, is illustrated in FIG.2. In the embodiment of FIG. 2, for each transmission speed, more thanone pair of helical cut gears are located on the input drive shaft forbeing engaged by more than one pair of helical cut gears located on theidler shaft.

The embodiment of FIG. 2 illustrates a two speed transmission using foreach transmission speed two pairs of paired helical cut gears on thedrive shaft and two pairs of paired helical cut gears on the drivenshaft. As discussed, in conjunction with the embodiment of FIG. 1, theangle of the helical cut of each gear of a gear pair is the same but inthe opposite sense or hand to one another. As in the embodiment of FIG.1, a driven gear would have a helical cut at the same angle but in theopposite sense or hand to the helical cut of an engaging drive gear. Asin the embodiment of FIG. 1, the transmission of the embodiment of FIG.2 includes an input drive shaft 1, two idler shafts 2 and 3, and anoutput shaft 4. Again, the input drive shaft would be connected to aprime mover such as an internal combustion engine (not illustrated).

Input drive shaft 1 has mounted thereon two pairs of paired helical cutgears 14 a, 14 b and 15 a, 15 b. Gears 14 a, 14 b and 15 a, 15 b are ofthe same size.

Mounted on idler shaft 2 are two pairs of driven helical cut gears 16 a,16 b and 17 a, 17 b. Mounted on idler shaft 3 are two pairs of drivenhelical cut gears 18 a, 18 b and 19 a, 19 b. As in the embodiment ofFIG. 1, idler shafts 2 an 3 are spline shafts so that the gears mountedon the idler shafts can more in the axial direction of the idler shaftas well as transmit force to the idler shafts for rotation of the idlershafts. Again, in preferred embodiments, a member, such as collar 21,(illustrated only between gears, 18 a, 18 b) would be disposed betweengears 16 a, 16 b; 17 a, 17 b; 18 a, 18 b; and 19 a, 19 b; to prevent thegear pairs from abutting against one another when created thrust forcescauses the gear pair to move toward one another on the idler shaft. Thereasons for this have been previously discussed.

In the embodiment of FIG. 2, for the drive helical cut gear pairsmounted on input drive shaft 1, only the two outermost gears of the gearpairs used for each transmission speed are restrained from axialmovement on the input drive shaft 1. Thus, in the FIG. 2 illustration,gears 14 a and 15 b are restrained from axial movement on input driveshaft 1. Gears 14 b and 15 b are mounted for axial movement on inputdrive shaft 2. Thus, input drive shaft 1 could be a spline shaft in therange of contemplated axial movement of gears 14 b and 15 a. Forconvenience, the entire input drive shaft 1 could be a spline shaft.Gears 14 a and 15 b could be restrained from axial movement on thespline input drive shaft 1 by a retainer member 50 being fixedly mountedto the input drive shaft 1 on the side of gear 14 a facing first end 31and a retainer member 51 being fixedly mounted on input drive shaft 1 onthe side of gear 15 b facing second end 32.

Helical cut drive gear pair 14 a, 14 b have a helical cut such thatgears 14 a and 14 b move away from each other in the axial direction ofthe input drive shaft by thrust forces created by rotation of inputdrive shaft 1 by the prime mover and engagement and mating with a pairof helical cut gears on an idler shaft. Likewise, helical cut drive gearpair 15 a, 15 b have a helical cut which cause them to separate or moveaway from one another in the axial direction of the input drive shaft 1.Since gear 14 a only moves toward first end 31 of input drive shaft 1and since gear 15 b only moves toward the second end 32 of input driveshaft 1 due to rotation of input drive shaft 1 by the prime mover, it issufficient to restrain the axial movement of gears 14 a and 15 b by thepreviously discussed retainer members 50 and 51.

Drive shaft collar member 53 is disposed between gears 14 b and 15 a. Itis sufficient that drive shaft collar member 53 be a cylindrical shapedmember surrounding the splined portion of input drive shaft 1 in a looseenough manner so as to permit drive shaft collar member 53 to movefreely in the axial direction of input drive shaft 1. Since thrustforces cause gear 14 b to move away or separate from gear 14 a in theaxial direction and cause gear 15 a to move away or separate from gear14 b in the axial direction, gears 14 b and 15 a first move toward oneanother in the axial direction of input drive shaft 1 and press againstone another or bear in compression against one another in the axialdirection through drive shaft collar member 53. This causes gears 14 band 15 a to move together in the axial direction of input drive shaft 1so, in the illustrated embodiment of FIG. 2, they center themselves onengaged and mating driven gears 18 b and 19 a on idler shaft 3. FIG. 3is a cross-section along line 3—3 of FIG. 2 illustrating a cross-sectionof drive shaft collar member 53. It is also apparent that gear 14 b,gear 15 a, and drive shaft collar member 53 could be a unitary structuremachined from the same piece of metal stock.

Helical cut gears 18 a, 18 b, mounted on idler shaft 3, have a helicalcut opposite to the helical cut on gears 14 a, 14 b. Therefore, rotationof input drive shaft 1 and the engagement and mating of gears 18 a, 18 bwith gears 14 a, 14 b results in thrust forces that cause gears 18 a, 18b to move toward one another in the axial direction of idler shaft 3.Helical cut gears 19 a, 19 b, mounted on idler shaft 3, have a helicalcut opposite to the helical cut on gears 15 a, 15 b. Therefore, rotationof input drive shaft 1 and the engagement and mating of gears 19 a, 19 bwith gears 15 a, 15 b results in thrust forces that causes gears 19 a,19 b to move toward one another in the axial direction of idler shaft 3.

In operation in the illustrated embodiment of FIG. 2, gears 18 a, 18 bmove together in the axial direction of idler shaft 3 to centerthemselves on gears 14 a, 14 b and gears 19 a, 19 b move together in theaxial direction of idler shaft 3 to center themselves on gears 15 a, 15b. This action is in combination with the previously described action ofthe combined movement of gears 14 b and 15 a. This results in abalancing of loads and an approximate load sharing amongst gears.

The foregoing description with respect to gear pair 18 a, 18 b and gearpair 19 a, 19 b on idler shaft 3 and their relationship to the drivegears on the input drive shaft 1 applies to helical cut gear pair 16 a,16 b and helical cut gear pair 17 a, 17 b on idler shaft 2 and theirrelationship to the drive gears on the input drive shaft 1.

Gears in the embodiment of FIG. 2 could be engaged and disengaged usingmechanisms described in connection with the FIG. 1 embodiment.

Helical gear pair 14 a, 14 b and helical gear pair 15 a and 15 b oninput drive shaft 1 may be referred to a drive set. Gears 14 a, 14 b, 15a and 15 b would all have the same outside diameter. Gear 14 a could bereferred to as a first drive helical gear half and gear 14 b could bereferred to a second drive helical gear half Likewise, gear 15 a couldbe referred to as a first drive helical gear half and gear 15 b could bereferred to as second drive helical gear half.

More than two pairs of helical gears may be used in a drive set ofhelical gears. The actual number of helical gear pairs used in a driveset would depend on the needs of the design. If more than two pairs ofhelical gears are used in the drive set, the two outermost gears wouldbe restrained from axial movement along the input drive shaft 1. All ofthe remaining helical gears would be mounted on the input drive shaftfor axial movement along the drive shaft with a member, such as driveshaft collar member 53, located between adjacent interior gears whichmove toward one another in the axial direction of the drive shaft due torotation of the drive shaft and engagement and mating with a respectivedriven helical cut gear.

Helical gear pair 18 a, 18 b and helical gear pair 19 a, 19 b on idlershaft 3 may be referred to as driven set of helical gears. Gears 18 a,18 b, 19 a and 19 b would all have the same outside diameter. Gear 18 acould be referred to as a first driven helical gear half and gear 18 bcould be referred to as a second driven helical gear half. Likewise,gear 19 a could be referred to a first driven helical gear half and gear19 b could be referred to as a second driven helical gear half.

More than two pairs of helical gears may be used in a driven set ofhelical gears. Again the actual number of helical gear pairs used in adriven set would depend on the needs of the design. For a driven set ofhelical gears, all the helical gears would be mounted on an idler shaftfor axial movement on the idler shaft.

The number of pairs of helical gears in a drive set is equal to thenumber of pairs of helical gears in a driven set.

In the embodiment of FIG. 2, helical gear pair 16 a, 16 b and helicalgear pair 17 a, 17 b comprise another driven set of helical gears.

Two or more drive sets of helical gears may be provided on the inputdrive shaft. Likewise, two or more driven sets of helical gears may beprovided on each idler shaft. More than two idler shafts may be providedwith one or more driven sets of helical gears located on each idlershaft.

Likewise, there would be only one idler shaft, with at least two drivensets of helical gears on the idler shaft and at least two drive sets ofhelical gears provided on the input drive shaft.

The output shaft 4 and the output gear arrangement would be the same asdiscussed in conjunction with FIG. 1. For an embodiment such asdescribed in conjunction with FIG. 2, arrangements using multiple pairsof helical gears on the output shaft 4 may be useful.

Although preferred embodiments of the present invention have beendescribed in detail, it is apparent that modifications may be made byone skilled in the art within the spirit and scope of the presentinvention as defined in the claims.

What is claimed is:
 1. A multi-speed transmission comprising: a driveshaft having an axis; a first pair of helical cut drive gears mounted onsaid drive shaft for rotation by said drive shaft and restrained fromseparating from one another in the axial direction of said drive shaftmore than a preselected spaced apart distance; a first idler shaftdisposed parallel to said drive shaft, thereby having an axis parallelto the axis of said drive shaft; a first pair of helical cut drivengears mounted on said first idler shaft for rotating said first idlershaft when said first pair of helical cut driven gears mounted on saidfirst idler shaft selectively engage and mate said first pair of helicalcut drive gears mounted on said drive shaft; said first pair of helicalcut driven gears mounted on said first idler shaft being further mountedon said first idler shaft for axial movement on said first idler shaft;a second idler shaft disposed parallel to said drive shaft, therebyhaving an axis parallel to the axis of said drive shaft and parallel tothe axis of said first idler shaft; a first pair of helical cut drivengears mounted on said second idler shaft for rotating said second idlershaft when said first pair of helical cut driven gears mounted on saidsecond idler shaft selectively engage and mate said first pair ofhelical cut drive gears mounted on said drive shaft; said first pair ofhelical cut driven gears mounted on said second idler shaft beingfurther mounted on said second idler shaft for axial movement on saidsecond idler shaft; said helical cut on said first pair of drive gearsbeing opposite to said helical cut on said first pair of driven gearsmounted on said first idler shaft and being oriented to cause said firstpair of driven gears mounted on said first idler shaft to move towardone another in the axial direction of said first idler shaft when saidfirst pair of drive gears are selectively engaged and mated by saidfirst pair of driven gears mounted on said first idler shaft forrotation thereof; said helical cut on said first pair of drive gearsbeing opposite to said helical cut on said first pair of driven gearsmounted on said second idler shaft and being oriented to cause saidfirst pair of driven gears mounted on said second idler shaft to movetoward one another in the axial direction of said second idler shaftwhen said first pair of drive gears are selectively engaged and mated bysaid first pair of driven gears mounted on said second idler shaft forrotation thereof.
 2. A multi-speed transmission according to claim 1wherein a spacer member is disposed between each gear of said first pairof helical cut driven gears mounted on said first idler shaft andanother spacer member is disposed between each gear of said first pairof helical cut driven gears mounted on said second idler shaft.
 3. Amulti-speed transmission according to claim 1 wherein a plurality ofpairs of helical cut drive gears are mounted on said drive shaft forbeing selectively engaged by a plurality of respective pairs of helicalcut driven gears mounted on said first idler shaft and for beingselectively engaged by a plurality of respective pairs of helical cutdriven gears mounted on said second idler shaft.
 4. A multi-speedtransmission according to claim 1 wherein a plurality of idler shaftsare disposed parallel to said drive shaft, each idler shaft havingmounted thereon a plurality of pairs of helical cut driven gears forselectively engaging a plurality of respective pairs of helical cutdrive gears mounted on said drive shaft.
 5. A multi-speed transmissionaccording to claim 1 further comprising: an output shaft disposedparallel to said drive shaft, thereby having a axis parallel to the axisof said drive shaft and parallel to the axis of each idler shaft; a pairof helical cut driven gears mounted on said output shaft for rotatingsaid output shaft; a pair of helical cut output drive gears mounted onsaid first idler shaft for rotation by said first idler shaft andengaging said pair of helical cut driven gears mounted on said outputshaft; a pair of helical cut output drive gears mounted on said secondidler shaft for rotation by said second idler shaft and engaging saidpair of helical cut driven gears mounted on said output shaft.
 6. Amulti-speed transmission according to claim 5 further comprising: saidpair of helical cut output drive gears mounted on said first idler shafthas a different outside diameter than said pair of helical cut outputdrive gears mounted on said second idler shaft; and said output shaft islocated in a different plane than said first idler shaft and said secondidler shaft, with the axes of said output shaft and said first and saidsecond idler shafts remaining parallel to one another.
 7. A multi-speedtransmission comprising: a drive shaft having an axis; a first pair ofhelical cut drive gears mounted on said drive shaft for rotation by saiddrive shaft and restrained from separating from one another in the axialdirection of said drive shaft more than a preselected spaced apartdistance; a second pair of helical cut drive gears mounted on said driveshaft for rotation by said drive shaft and restrained from separatingfrom one another in the axial direction of said drive shaft more than apreselected spaced apart distance; a first idler shaft disposed parallelto said drive shaft, thereby having an axis parallel to the axis of saiddrive shaft; a first pair of helical cut driven gears mounted on saidfirst idler shaft for rotating said first idler shaft when said firstpair of helical cut driven gears mounted on said first idler shaftselectively engage and mate said first pair of helical cut drive gearsmounted on said drive shaft; said first pair of helical cut driven gearsmounted on said first idler shaft being further mounted on said firstidler shaft for axial movement on said first idler shaft; a second pairof helical cut driven gears mounted on said first idler shaft forrotating said first idler shaft when said second pair of helical cutdriven gears mounted on said first idler shaft selectively engage andmate said second pair of helical cut drive gears mounted on said driveshaft; said second pair of helical cut driven gears mounted on saidfirst idler shaft being further mounted on said first idler shaft foraxial movement on said first idler shaft; said helical cut on said firstpair of drive gears being opposite to said helical cut on said firstpair of driven gears mounted on said first idler shaft and beingoriented to cause said first pair of driven gears mounted on said firstidler shaft to move toward one another in the axial direction of saidfirst idler shaft when said first pair of drive gears are selectivelyengaged and mated by said first pair of driven gears mounted on saidfirst idler shaft for rotation thereof; said helical cut on said secondpair of drive gears being opposite to said helical cut on said secondpair of driven gears mounted on said first idler shaft and beingoriented to cause said second pair of driven gears mounted on said firstidler shaft to move toward one another in the axial direction of saidfirst idler shaft when said second pair of drive gears are selectivelyengaged and mated by said second pair of driven gears mounted on saidfirst idler shaft for rotation thereof.
 8. A multi-speed transmissionaccording to claim 7 wherein a spacer member is disposed between eachgear of said first pair of helical cut driven gears mounted on saidfirst idler shaft and another spacer member is disposed between eachgear of said second pair of helical cut driven gears mounted on saidfirst idler shaft.
 9. A multi-speed transmission according to claim 7wherein a plurality of pairs of helical cut drive gears are mounted onsaid drive shaft for being selectively engaged by a plurality ofrespective pairs of helical cut driven gears mounted on said first idlershaft.
 10. A multi-speed transmission comprising: a drive shaft havingan axis, a first end, and a second end; a drive set of helical cutgears, with each helical cut gear of said drive set mounted on saiddrive shaft for rotation by said drive shaft, said drive set of helicalgears comprising: a first pair of drive helical cut gears mounted onsaid drive shaft for rotation by said drive shaft including a firstdrive helical gear half and an adjacent second drive helical gear halfspaced from said first drive helical gear half toward the second end ofsaid drive shaft, said first drive helical gear half being restrainedfrom axial movement on said drive shaft in a direction toward said firstend of the drive shaft and said second drive helical gear half mountedon said drive shaft for axial movement on said drive shaft; another pairof drive helical cut gears mounted on said drive shaft spaced from saidfirst pair of drive helical cut gears toward said second end of saiddrive shaft, said another pair of helical gears including a first drivehelical gear half and an adjacent second drive helical gear half spacedfrom said first drive helical gear half toward the second end of saiddrive shaft, said first drive helical gear half being mounted on saiddrive shaft for axial movement on said drive shaft and said second drivehelical gear half being restrained from axial movement on said driveshaft in a direction toward said second end of said drive shaft; a driveshaft spacer member disposed between drive helical gear halves mountedon said drive shaft for axial movement on said drive shaft which movetoward one another in the axial direction of said drive shaft due torotation of said drive shaft and engagement and mating with a respectivedriven helical gear half; a first idler shaft having a first end and asecond end and disposed parallel to said drive shaft, thereby having anaxis parallel to the axis of said drive shaft; a driven set of helicalcut gears mount on said first idler shaft, with each helical cut gear ofsaid driven set mounted on said first idler shaft for selectivelyrotating said first idler shaft, said driven set of helical cut gearsmount on said first idler shaft comprising: a first pair of drivenhelical cut gears mounted on said first idler shaft for rotating saidfirst idler shaft when selectively engaging and mating said first pairof drive helical cut gears of said drive set, said first pair of drivenhelical cut gears including a first driven helical gear half and anadjacent second driven helical gear half, said first and second helicalgear halves being mounted on said first idler shaft for axial movementon said first idler shaft; another pair of driven helical cut gearsmounted on said first idler shaft for rotating said first idler shaftwhen selectively engaging and mating said another pair of drive helicalcut gears of said drive set, said another pair of driven helical cutgears being spaced from said first pair of driven helical gears towardsaid second end of said first idler shaft, said another pair of drivenhelical cut gears including a first driven helical gear half and anadjacent second driven helical gear half, said first and second drivenhelical gear halves being mounted on said first idler shaft for axialmovement on said first idler shaft; a second idler shaft having a firstend and a second end and disposed parallel to the axis of said driveshaft, thereby having an axis parallel to the axis of the drive shaftand the axis of the first idler shaft; a driven set of helical cut gearsmounted on said second idler shaft, with each helical cut gear of saiddriven set mounted on said second idler for selectively rotating saidsecond idler shaft, said driven set of helical cut gears mounted on saidsecond idler shaft comprising: a first pair of driven helical cut gearsmounted on said second idler shaft for rotating said second idler shaftwhen selectively engaging and mating said first pair of drive helicalcut gears of said drive set, said first pair of driven helical cut gearsincluding a first driven helical gear half and an adjacent second drivenhelical gear half, said first and second helical gear halves beingmounted on said second idler shaft for axial movement on said secondidler shaft; another pair of driven helical cut gears mounted on saidsecond idler shaft for rotating said second idler shaft when selectivelyengaging and mating said another pair of drive helical cut gears of saiddrive set, said another pair of driven helical cut gears being spacedfrom said first pair of driven helical cut gears toward said second endof said second idler shaft, said another pair of driven helical cutgears including a first driven helical gear half and an adjacent seconddriven helical gear half, said first and second helical gear halvesbeing mounted on said second idler shaft for axial movement on saidsecond idler shaft; said helical cut on said drive set first pair andanother pair of drive helical gear halves being opposite to said helicalcut on said first idler shaft driven set first pair and another pair ofdriven helical gear halves and being oriented to cause first and seconddriven helical gear halves of each pair of driven helical gears to movetoward one another in the axial direction of said first idler shaft andto cause first and second drive helical gears halves of each pair ofdrive helical gears to separate from one another in the axial directionof the drive shaft when said drive pairs of helical cut gears of thedrive set are selectively engaged and mated by said driven pairs ofhelical cut gears of said driven set mounted on said first idler shaft;said helical cut on said drive set first pair and another pair of drivehelical gear halves being opposite to said helical cut on said secondidler shaft driven set first pair and another pair of driven helicalgear halves and being oriented to cause first and second driven helicalgear halves of each pair of driven helical gears to move toward oneanother in the axial direction of said second idler shaft and to causefirst and second drive helical gear halves of each pair of drive helicalgears to separate from one another in the axial direction of the driveshaft when said drive pairs of helical cut gears of the drive set areselectively engaged and mated by said driven pairs of helical cut gearsof said driven set mounted on said second idler shaft.
 11. A multi-speedtransmission according to claim 10 wherein a spacer member is disposedbetween each driven helical gear half of each pair of driven helical cutgears of the driven set mounted on the first idler shaft and a spacermember is disposed between each driven helical gear half of each pair ofdriven helical cut gears of the driven set mounted on the second idlershaft.
 12. A multi-speed transmission according to claim 10 wherein aplurality of drive sets of helical cut gears are mounted on said driveshaft for being selectively engaged by a plurality of respective drivensets of helical cut gears mounted on said first idler shaft and forbeing selectively engaged by a plurality of respective driven sets ofhelical cut gears mounted on said second idler shaft.
 13. A multi-speedtransmission according to claim 10 wherein a plurality of idler shaftsare disposed parallel to said drive shaft and each idler shaft hasmounted thereon at least on driven set of helical cut gears.
 14. Amulti-speed transmission comprising: a drive shaft having an axis, afirst end, and a second end; at least two drive sets of helical cutgears, with each helical cut gear of each drive set mounted on saiddrive shaft for rotation by said drive shaft, each drive set of helicalgears comprising: a first pair of drive helical cut gears mounted onsaid drive shaft for rotation by said drive shaft including a firstdrive helical gear half and an adjacent second drive helical gear halfspaced from said first drive helical gear half toward the second end ofsaid drive shaft, said first drive helical gear half being restrainedfrom axial movement on said drive shaft in a direction toward said firstend of the drive shaft and said second drive helical gear half mountedon said drive shaft for axial movement on said drive shaft; another pairof drive helical cut gears mounted on said drive shaft spaced from saidfirst pair of drive helical cut gears toward said second end of saiddrive shaft, said another pair of helical gears including a first drivehelical gear half and an adjacent second drive helical gear half spacedfrom said first drive helical gear half toward the second end of saiddrive shaft, said first drive helical gear half being mounted on saiddrive shaft for axial movement on said drive shaft and said second drivehelical gear half being restrained from axial movement on said driveshaft in a direction toward said second end of said drive shaft; a driveshaft spacer member disposed between drive helical gear halves mountedon said drive shaft for axial movement on said drive shaft which movetoward one another in the axial direction of said drive shaft due torotation of said drive shaft and engagement and mating with a respectivedriven helical gear half; a first idler shaft having a first end and asecond end and disposed parallel to said drive shaft, thereby having anaxis parallel to the axis of said drive shaft; at least two driven setsof helical cut gears mount on said first idler shaft, with each helicalcut gear of each driven set mounted on said first idler shaft forselectively rotating said first idler shaft, each driven set of helicalcut gears mount on said first idler shaft comprising: a first pair ofdriven helical cut gears mounted on said first idler shaft for rotatingsaid first idler shaft when selectively engaging and mating said firstpair of drive helical cut gears of said drive set, said first pair ofdriven helical cut gears including a first driven helical gear half andan adjacent second driven helical gear half, said first and secondhelical gear halves being mounted on said first idler shaft for axialmovement on said first idler shaft; another pair of driven helical cutgears mounted on said first idler shaft for rotating said first idlershaft when selectively engaging and mating said another pair of drivehelical cut gears of said drive set, said another pair of driven helicalcut gears being spaced from said first pair of driven helical gearstoward said second end of said first idler shaft, said another pair ofdriven helical cut gears including a first driven helical gear half andan adjacent second driven helical gear half, said first and seconddriver, helical gear halves being mounted on said first idler shaft foraxial movement on said first idler shaft; said helical cut on each driveset first pair and another pair of drive helical gear halves beingopposite to said helical cut on each first idler shaft driven set firstpair and another pair of driven helical gear halves and being orientedto cause first and second driven helical gear halves of each pair ofdriven helical gears to move toward one another in the axial directionof said first idler shaft and to cause first and second drive helicalgear halves of each pair of drive helical gears to separate from oneanother in the axial direction of the drive shaft when said drive pairsof helical cut gears of a selected drive set are selectively engaged andmated by said driven pairs of helical cut gears of a selected driven setmounted on said first idler shaft.